We will need to do a premier support ticket to go through this together.
In order to be truly proficient in creating web sites you need to master quite a few concepts that work together:
4) Database Design
Depending on where you are least proficient, there are many books you can read about any of these topics. Using our tools puts these 6 concepts together, but an understanding of the underlying technologies is always helpful particularly when debugging when things go wrong. I'll attempt to answer your questions here, but really a 1 hour training to go over these would probably be necessary to fix them efficiently.
If you want help through the forums I'd suggest:
1) Post only one issue at a time and not three
2) Include a URL and steps to reproduce the problem so I can view it on the web directly
3) Provide FTP access if I don't already have it so I can look at your files
4) Verify that the data in the database is correct and describe how it works since I won't likely have access to your phpMyAdmin
I'm not entirely confident that the issue is only in the php code and not a data integrity issue. I'd first confirm that the database has the correct records to begin with.
If the database is correct, then it is probably a matter of writing the correct SQL statement. Most likely adding a GROUP BY clause, but I'd need to talk it through with you to see what you are trying to achieve and how the database is structured.
The multiple repeat issue is a matter of adding a GROUP BY in your recordset sql statement probably. The error on the update is a missing url parameter most likely.
The missing record after update is probably because you aren't inserting the correct record in a joined table and your recordset uses an INNER JOIN. If the associated record in a related table is missing then the result won't be found.